Underground storage tanks employed in gasoline service stations are conventionally refilled by means of a filler pipe which projects upwardly from the buried tank into a relatively shallow manhole in the concrete apron of the service station. To provide convenient access to couple and uncouple the supply hose of the supply truck to the top of the filler pipe, the sides of the manhole are spaced a reasonable distance from the filler pipe. The bottom of the manhole is normally defined by fill dirt or a mixture of pea gravel.
Because of the relatively large capacity of the underground storage tanks, refill fuel is pumped into the tank at a fairly substantial flow rate which may result in overfilling the tank. Carelessness in uncoupling the supply hose, where the hose has not been completely drained, will result in spillage of gasoline into the fill surrounding the filler pipe when the hose is uncoupled.
Contamination of the soil by such spillage is obviously undesirable and various states now require that protective devices which will prevent such spillage from reaching the soil be employed.
Typically, these protection devices take the form of a closed tank surrounding the upper end of the filler pipe which will capture the spilled fuel, store the captured fuel and conduct the captured fuel to the storage tank when the tank has room to receive the fuel. Such protective tanks will have a capacity of approximately 35 gallons to enable spillage to be stored at least temporarily in the event the spillage results from overfilling of the main storage tank.
To afford sufficient access to the top of the filler pipe, such spillage capture tanks are normally formed with a relatively large diameter cylindrical stack which surrounds the upper end of the filler pipe and provides a sufficient clearance radially from the filler pipe to make coupling and uncoupling of the supply hose to the filler pipe convenient. This enlarged stack further is of a sufficient diameter to assure that all spillage normally encountered will be captured.
Because the top of this stack must be located below the surface of the concrete and the manhole cover does not provide a watertight seal, it is necessary that a cover be mounted upon the top of the capture tank stack to seal the interior of the capture tanks at all times when the cover is not opened during filling operations. This seal is necessary to prevent entry of ground water, as in the case of heavy rain, into the capture tank and to prevent the escape of volatile fumes from the capture tank when it is storing spilled gasoline.
The present invention is especially directed to a locking lid assembly for accomplishing this last purpose which will provide a compressed and completely adequate seal when the lid is closed while at the same time providing an easy release so that the lid may be easily opened for access to the filler pipe.